Reactive oxygen species are produced by biological reactions during normal metabolic processes in the human body. However, the accumulation of reactive oxygen species or the production of excessive amounts of reactive oxygen species is harmful to most organisms, and this condition is known as oxidative stress. Oxidative stress is known to cause various diseases in cells and tissues. As known so far, gastrointestinal diseases, diabetes, cancer, cardiovascular diseases, neurodegenerative diseases, and the like are caused by oxidative stress. As a physiological action that inhibits the production of free radicals in vivo in order to prevent this oxidative stress, the mechanism of action that donates electrons to oxidative free radicals to inhibit oxidation or to convert superoxide anion radicals into normal oxides is known.
As this oxidative stress was found to be an important factor that causes various diseases including aging, studies have been actively conducted to develop antioxidant agents that remove reactive oxygen species in vivo. Many studies have been conducted on antioxidant enzymes, such as superoxide dismutase (SOD), catalase, peroxidase, glutathione and the like, which are capable of controlling reactive oxygen species, and low molecular antioxidant substances, such as vitamin C (ascorbic acid), vitamin E (tocopherol) and the like, which are derived from natural materials. In addition, many synthetic antioxidants, such as BHA (butylatedhydroxyanisole), BHT (butylatedhydroxytoluene) and NDGA (nordihydroguaiaretic acid), have also been developed and used in the pharmaceutical and food fields.
However, natural antioxidant substances derived from natural materials have problems in that, because these antioxidant substances do not have potent antioxidant effects, they should be used in large amounts in order to provide substantial antioxidant effects, and accordingly the use of these antioxidant substances is expensive and has low economic efficiency. Meanwhile, although chemically synthesized antioxidant substances exhibit excellent antioxidant effects compared to the natural antioxidant substances, they have a new problem in that serious and mild side effects are caused in the humanbody, and thus the use thereof is limited.
Meanwhile, the excessive accumulation of lipids on blood vessel walls reduces the size of blood vessels, and causes atherosclerosis through inflammatory responses. This can cause coronary heart diseases, cerebrovascular diseases, peripheral vascular occlusion, or the like. In addition, excessive blood lipids can accumulate in liver tissue, causing fatty liver.
Methods used so far to reduce blood lipid levels include a dietary therapy that reduces the intake of foods containing large amounts of cholesterols or fats, as well as exercise therapy and drug therapy. However, dietary therapy or exercise therapy is difficult to manage strictly and implement, and the therapeutic effect thereof is also limited.
Meanwhile, drugs that have been developed so farto reduce lipid levels include: bile acid binding resins; cholesterol level-lowering drugs, such as inhibitors of HMF-CoA reductase, which is an enzyme important in cholesterol synthesis; and triglyceride lowering drugs, such as fabric acid derivatives, nicotinic acid, etc. However, these drugs were reported to cause side effects, including hepatotoxicity, gastrointestinal disorders, carcinogenesis, and the like. Accordingly, there is an urgent need to develop drugs which may be used to treat hyperlipidemia and related diseases by effectively lowering blood lipid levels and which cause less side effects.